Mixing devices

ABSTRACT

A mixing device comprising rotor and stator elements wherein a screw conveyor is mounted on the rotor shaft and, upon rotation of the shaft, conveys material towards the inlet to the stator element. Associated with the conveyor are stationary guide plates which assist in providing an increased flow of material to the stator element.

United States Patent Love Jan. 1, 1974 MIXING DEVICES 2,875,897 3/1959Booth 259 96 x [75] Inventor: Gordon David Love, Waterside, England3,669,414 6/1972 Love [73] Assignee: Silverson Machines Limited,

Water ide, E l d Primary Examiner-Billy J. Wilhite AssistantExaminerAlan I. Cantor [22] Filed: 1971 Att0rneyDelio & Montgomery [2!]Appl. No.: 213,147

[57] ABSTRACT [52] U.S. Cl. 259/6, 259/96 A mi ing device comprisingrotor and stator elements [51] Int. Cl. B0lf 3/12, BOlf 5/16 wherein ascrew conveyor is mounted n the t r [58] Field of Search 259/8, 23, 24,43, shaft n p rotation of the shaft, conveys material 259/44, 66, 67, 96towards the inlet to the stator element. Associated with the conveyorare stationary guide plates which [56] References Cited assist inproviding an increased flow of material to the UNITED STATES PATENTS4/1959 Willems 259/96 X stator element.

8 Claims, 2 Drawing Figures MIXING DEVICES This invention relates tomixing devices.

The present invention includes a mixing device comprising co-operatingrotor and stator elements of which the stator element has an inlet atone end thereof and outlet aperture means in a side wall thereof and therotor element comprises a bladed impeller mounted on an elongated shaftand adapted, upon rotation, to expel material within the stator elementoutwardly via the outlet aperture means, wherein conveyor means aremounted on the rotor shaft outside the stator element and are adapted,upon rotation of the shaft, to convey material in directions generallyparallel with the shaft towards the inlet to the stator element.

Preferably, the conveyor means comprise a helical screw conveyor.

Preferably, guide means, secured relative to the stator element, arearranged adjacent to the conveyor means, the guide means serving toprevent or substantially prevent rotation of material adjacent to theconveyor means, thereby to provide an increased flow of material in thesaid directionsgenerally parallel with the shaft. V

The guide means may comprise a plurality of guide elements respectivelydisposed at locatio'ns angularly spaced about the axis of the rotorshaft, each guide element extending generally parallel with the rotorshaft and extending outwardly from a location adjacent to the conveyormeans at an angle which is inclined to the radial direction at thatlocation.

Suitably the device comprises a further mixing head co-operating rotorand stator elements, the rotor element of the further mixing head beingmounted on the said rotor shaft and each stator element in the devicebeing arranged with the inlet thereto facing in a direction away fromthe other stator element.

The invention will now be described,'by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a side elevation, partly in section, of a mixing deviceaccording to the invention; and

FIG. 2 is a plan view from below of the device of FIG. 1.

The mixing device of FIGS. 1 and 2 is suitable for mixing together twoviscous liquids or for mixing a liquid and particles of a solid whichare not readily wetted and tend to float on the surface of the liquid.

Included in the device is an upper mixing or disintegrating head 1having a rotor element 3 and cooperating stator element 5 and a lowermixing head 7 having co-operating rotor and stator elements 9 and l 1,respectively. The rotor elements 3 and 9 are mounted on a common rotorshaft 13 and the stator elements 5 and 11 are mounted on a commonsupporting plate 15.

In use, the device is immersed in material within a mixing vessel (notshown), the supporting plate being pendantly supported from the casingof a motor (not shown) above the vessel and the common shaft 13 beingcoupled to an output shaft of the motor. When the motor is energised theupper rotor element 3 serves to-drive material radially outwardlythrough the associated stator element 5 and to cause a downwards flow ofmaterial into the element 5 to replace that expelled. The lower rotorelement likewise expels material radially outwardly from the associatedstator element 11. This material is replaced by an upwards flow fromconveyor means, generally designated 17, which are provided on a lowerend of the rotor shaft 13, and associated guide means, generallydesignated 19, which depend from the supporting plate 15.

In the present device the supporting plate 15 is pendantly supportedfrom the motor casing by four pillars 21 and is formed with a central,apertured boss 23 through which the rotor shaft 13 extends.

The stator element 11 of the lower head 7 has an apertured, cylindricalside wall 25 formed with an outer flange 27 at its upper end. The flange27 is bolted to the under-surface of the supporting plate 15, coaxiallyof the apertured boss 23; and the lower end of the wall 25 is open andprovides an inlet 28 to the stator element 11.

The rotor element 9 of the lower head 7 consists of a rotor plate 29 andfour rotor blades 31 which depend from an under surface of the plate 29.The rotor element 9 is secured to a section of the rotor shaft 13 whichis disposed within the lower stator element 11. Each rotor blade 31extends outwardly from the rotor shaft 13 to a radial location adjacentto an inner surface of the cylindrical sidewall 25 of the stator element11.

The conveyor means 17 of the present device is formed of a helical screwconveyor 33 mounted on a sleeve 35. The sleeve 35 is secured to a lowerend of the rotor shaft 13 below the stator element 11 of the lowermixing head 7.

Associated with the conveyor means 17 are four upstanding guide plates37 which form the abovementioned guide means 19. The plates 37 aredisposed at equi-angularly spaced locations about the axis of the rotorshaft 13, with each plate 37 secured at its upper end to a bracket 39which is bolted to the supporting plate 15. As viewed in plan, eachguide plate 37 extends from a location adjacent to the screw conveyor 33outwardly in a direction which is inclined to the radial direction atthat location.

The stator element 5 of the upper mixing head 1 is mounted on pillars 41upstanding from the common supporting plate 15. As in the case of thelower head 7, the stator element 5 is formed of an apertured,cylindrical side wall 43 having a flange 45 at one end thereof. Thestator element 5 is arranged with the flange 45 lowermost and secured tothe upper, ends of the supporting pillars 41. The upper end of the sidewall 43 is open and provides an inlet 44 to the stator element 5.

The rotor element 3 of the upper head 1 likewise corresponds to therotor element 9 of the lower head 7, being formed of a rotor plate 47and four rotor blades 49. The rotor element 3 is secured to a section ofthe rotor shaft 13 within the upper stator element 5 with the blades 49upstanding from the rotor plate 47.

In use, the present device is supported by a driving motor in the mannerset out above and the upper and lower mixing heads 1 and 7,respectively, the screw conveyor 33 and the guide plates 37 are immersedin material within the mixing vessel.

When the motor is energised the rotating blades 49 and 31 of rotorelements 1 and 7, respectively, serve to force material radiallyoutwardly through the apertures in the side wall 43 or 25 of theassociated stator element 5 or 11. As the material passes between theblades 49 or 31 and the side wall 43 or 25 and through the apertures inthe side wall it is subjected to thorough mixing. Any solid particlespresent are also subjected to disintegration.

Material expelled from the upper stator element 5 is replaced by adownwards flow of material from the top of the mixing vessel into theinlet 44 at the upper end of the stator element 5. This downwards flowarises from the vortex effect of the upper rotor element 3 and isparticularly important in mixing a solid which is not readily wettedwith a liquid.

In the absence of the screw conveyor 33 and guide 37 material expelledfrom the lower stator element 11 could only be replaced by a similar,upwards flow from the bottom of the mixing vessel. ln mixing viscousliquids, however, it is found that the upwards, replacement flow cannotkeep pace with the rate at which material is expelled from the lowerstator element 11. As a result, a region of reduced pressure is formedwithin the stator element 11 and the effective rate of mixing anddisintegration is greatly reduced.

The screw conveyor 33 serves to provide an upwards replacement flow ofmaterial towards the inlet 28 to the lower stator element 11 which isequal, or substantially equal, to the rate at which material isexpelled. This is true even for viscous liquids.

In the absence of the guide plates 37 rotation of the screw conveyor 33would tend to cause rotation of material adjacent to the material whichis actually engaged by the conveyor. The guide plates 37 prevent, orsubstantially prevent, rotation of this adjacent material. This reducesslippage of material on the conveyor 33, thereby producing an increasedrate of supply of material upwardly towards the inlet 28.

lt will be appreciated that the helical screw conveyor 33 could bereplaced by other forms of conveyor. For example, the helical screwcould be broken at equiaxially spaced locations or it could be replacedby a series of propellers arranged to provide a flow of materialgenerally parallel with the shaft 13.

I claim:

1. A mixing device comprising: a first mixing head having co-operatingrotor and stator elements of which the stator element has an inlet atone end thereof and outlet aperture means in a side wall thereof and therotor element comprises a bladed impeller mounted on an elongated shaftand adapted, upon rotation, to expel material within the stator elementoutwardly via the outlet aperture means, and conveyor means mounted onthe rotor shaft outside the stator element and adapted, upon rotation ofthe shaft, to convey material in directions generally parallel with theshaft towards the inlet to the stator element, said conveyor meanscomprising a helical screw conveyor.

2. A mixing device as claimed in claim 1, further including guide meanssecured relative to the stator element and arranged adjacent to theconveyor means, the guide means being adapted to prevent orsubstantially prevent rotation of material adjacent to the conveyormeans, thereby to provide an increased flow of material in the saiddirections generally parallel with the shaft.

3. A mixing device as claimed in claim 2, wherein the guide meanscomprise a plurality of guide elements respectively disposed atlocations angularly spaced about the axis of the rotor shaft, each guideelement extending generally parallel with the rotor shaft and extendingoutwardly from a location adjacent to the conveyor means at an anglewhich is inclined to the radial direction at that location.

4. A mixing device comprising: a first mixing head having co-operatingrotor and stator elements of which the stator element has an inlet atone end thereof and outlet aperture means in a side wall thereof and therotor element comprises a bladed impeller mounted on an elongated shaftand adapted, upon rotation, to expel material within the stator elementoutwardly via the outlet aperture means, conveyor means mounted on therotor shaft outside the stator element and adapted, upon rotation of theshaft, to convey material in directions generally parallel with theshaft towards the inlet to the stator element, and a second mixing headhaving co-operating rotor and stator elements, the rotor element of thesecond mixing head being mounted on the said rotor shaft and each statorelement in the device being arranged with the inlet thereto facing in adirection away from the other stator element.

5. A mixing device as claimed in claim 4, wherein said conveyor meanscomprises a helical screw conveyor.

6. A mixing device as claimed in claim 4, further including guide meanssecured relative to the stator element of said first mixing head andarranged adjacent to the conveyor means, the guide means being adaptedto prevent or substantially prevent rotation of material adjacent to theconveyor means, thereby to provide an increased flow of material in thesaid directions generally parallel with the shaft.

7. A mixing device as claimed in claim 6, wherein the guide meanscomprise a plurality of guide elements respectively disposed atlocations angularly spaced about the axis of the rotor shaft, each guideelement extending generally parallel with the rotor shaft and extendingoutwardly from a location adjacent to the conveyor means at an anglewhich is inclined to the radial direction at that location.

8. A mixing device comprising: a pair of mixing heads each having arotor and a stator, said stator having an inlet at one end and outletaperture means at the side thereof, wherein the rotors are mounted ataxially spaced locations on a common shaft and each stator is arrangedwith the inlet thereof facing in an axial direction away from the otherstator.

1. A mixing device comprising: a first mixing head having cooperating rotor and stator elements of which the stator element has an inlet at one end thereof and outlet aperture means in a side wall thereof and the rotor element comprises a bladed impeller mounted on an elongated shaft and adapted, upon rotation, to expel material within the stator element outwardly via the outlet aperture means, and conveyor means mounted on the rotor shaft outside the stator element and adapted, upon rotation of the shaft, to convey material in directions generally parallel with the shaft towards the inlet to the stator element, said conveyor means comprising a helical screw conveyor.
 2. A mixing device as claimed in claim 1, further including guide means secured relative to the stator element and arranged adjacent to the conveyor means, the guide means being adapted to prevent or substantially prevent rotation of material adjacent to the conveyor means, thereby to provide an increased flow of material in the said directions generally parallel with the shaft.
 3. A mixing device as claimed in claim 2, wherein the guide means comprise a plurality of guide elements respectively disposed at locations angularly spaced about the axis of the rotor shaft, each guide element extending generally parallel with the rotor shaft and extending outwardly from a location adjacent to the conveyor means at an angle which is inclined to the radial direction at that location.
 4. A mixing device comprising: a first mixing head having co-operating rotor and stator elements of which the stator element has an inlet at one end thereof and outlet aperture means in a side wall thereof and the rotor element comprises a bladed impeller mounted on an elongated shaft and adapted, upon rotation, to expel material within the stator element outwardly via the outlet aperture means, conveyor means mounted on the rotor shaft outside the stator element and adapted, upon rotation of the shaft, to convey material in directions generally parallel with the shaft towards the inlet to the stator element, and a second mixing head having co-operating rotor and stator elements, the rotor element of the second mixing head being mounted on the said rotor shaft and each stator element in the device being arranged with the inlet thereto facing in a direction away from the other stator element.
 5. A mixing device as claimed in claim 4, wherein said conveyor means comprises a helical screw conveyor.
 6. A mixing device as claimed in claim 4, further including guide meaNs secured relative to the stator element of said first mixing head and arranged adjacent to the conveyor means, the guide means being adapted to prevent or substantially prevent rotation of material adjacent to the conveyor means, thereby to provide an increased flow of material in the said directions generally parallel with the shaft.
 7. A mixing device as claimed in claim 6, wherein the guide means comprise a plurality of guide elements respectively disposed at locations angularly spaced about the axis of the rotor shaft, each guide element extending generally parallel with the rotor shaft and extending outwardly from a location adjacent to the conveyor means at an angle which is inclined to the radial direction at that location.
 8. A mixing device comprising: a pair of mixing heads each having a rotor and a stator, said stator having an inlet at one end and outlet aperture means at the side thereof, wherein the rotors are mounted at axially spaced locations on a common shaft and each stator is arranged with the inlet thereof facing in an axial direction away from the other stator. 